Definitions

• Haploid :

  • the presence of a single set of chromosomes in an organisms cells
• Diploid :

  • the presence of two complete sets of chromosomes in an organisms cells, with each parent contributing a chromosome to each pair
• Gamete :

  • a haploid sex cell
  • eg ova, sperm, pollen
• Homologous Pairs :

  • two chromosomes in a pair - normally one inherited from the mother and one from the father
• Bivalent :

  • the association of two replicated homologous chromosomes having exchanged DNA strand in at least one site called chiasmata
• Chromsomes :

  • coiled and condensed DNA
• Chiasmata :

  • a structure that forms between a pair of homologous chromosomes by crossover recombination
• Centromere :

  • the region which separates a chromatid into two arms
• Centrosome :

  • a cellular structure that produces spindle fibres and pulls homologous pairs/ chromatids apart during cell division
• Chromatin :

  • a mixture of DNA and protein that form the chromosomes found in the cells of humans and other higher organisms
• Chromatid :

  • one of the two identical halves of a chromosome that has been replicated in preparation for cell division
• Sister chromatids :

  • the two copies of a chromosome